A new take on carbon capture

by Zach Winn | MIT News
Boston MA (SPX) Nov 26, 2025

If there was one thing Cameron Halliday SM '19, MBA '22, PhD '22 was exceptional at during the early days of his PhD at MIT, it was producing the same graph over and over again. Unfortunately for Halliday, the graph measured various materials' ability to absorb CO2 at high temperatures over time - and it always pointed down and to the right. That meant the materials lost their ability to capture the molecules responsible for warming our climate.

At least Halliday wasn't alone: For many years, researchers have tried and mostly failed to find materials that could reliably absorb CO2 at the super-high temperatures of industrial furnaces, kilns, and boilers. Halliday's goal was to find something that lasted a little longer.

Then in 2019, he put a type of molten salt called lithium-sodium ortho-borate through his tests. The salts absorbed more than 95 percent of the CO2. And for the first time, the graph showed almost no degradation over 50 cycles. The same was true after 100 cycles. Then 1,000.

"I honestly don't know if we ever expected to completely solve the problem," Halliday says. "We just expected to improve the system. It took another two months to figure out why it worked."

The researchers discovered the salts behave like a liquid at high temperatures, which avoids the brittle cracking responsible for the degradation of many solid materials.

"I remember walking home over the Mass Ave bridge at 5 a.m. with all the morning runners going by me," Halliday recalls. "That was the moment when I realized what this meant. Since then, it's been about proving it works at larger scales. We've just been building the next scaled-up version, proving it still works, building a bigger version, proving that out, until we reach the ultimate goal of deploying this everywhere."

Today, Halliday is the co-founder and CEO of Mantel, a company building systems to capture carbon dioxide at large industrial sites of all types. Although a lot of people think the carbon capture industry is a dead end, Halliday doesn't give up so easily, and he's got a growing corpus of performance data to keep him encouraged.

Mantel's system can be added on to the machines of power stations and factories making cement, steel, paper and pulp, oil and gas, and more, reducing their carbon emissions by around 95 percent. Instead of being released into the atmosphere, the emitted CO2 is channeled into Mantel's system, where the company's salts are sprayed out from something that looks like a shower head. The CO2 diffuses through the molten salts in a reaction that can be reversed through further temperature increases, so the salts boil off pure CO2 that can be transported for use or stored underground.

A key difference from other carbon capture methods that have struggled to be profitable is that Mantel uses the heat from its process to generate steam for customers by combining it with water in another part of its system. Mantel says delivering steam, which is used to drive many common industrial processes, lets its system work with just 3 percent of the net energy that state-of-the-art carbon capture systems require.

"We're still consuming energy, but we get most of it back as steam, whereas the incumbent technology only consumes steam," says Halliday, who co-founded Mantel with Sean Robertson PhD '22 and Danielle Rapson. "That steam is a useful revenue stream, so we can turn carbon capture from a waste management process into a value creation process for our customer's core business - whether that's a power station using steam to make electricity, or oil and gas refineries. It completely changes the economics of carbon capture."

From science to startup

Halliday's first exposure to MIT came in 2016 when he cold emailed Alan Hatton, MIT's Ralph Landau Professor of Chemical Engineering Practice, asking if he could come to his lab for the summer and work on research into carbon capture.

"He invited me, but he didn't put me on that project," Halliday recalls. "At the end of the summer he said, 'You should consider coming back and doing a PhD.'"

Halliday enrolled in a joint PhD-MBA program the following year.

"I really wanted to work on something that had an impact," Halliday says. "The dual PhD-MBA program has some deep technical academic elements to it, but you also work with a company for two months, so you use a lot of what you learn in the real world."

Halliday worked on a few different research projects in Hatton's lab early on, all three of which eventually turned into companies. The one that he stuck with explored ways to make carbon capture more energy efficient by working at the high temperatures common at emissions-heavy industrial sites.

Halliday ran into the same problems as past researchers with materials degrading at such extreme conditions.

"It was the big limiter for the technology," Halliday recalls.

Then Halliday ran his successful experiment with molten borate salts in 2019. The MBA portion of his program began soon after, and Halliday decided to use that time to commercialize the technology. Part of that occurred in Course 15.366 (Climate and Energy Ventures), where Halliday met his co-founders. As it happens, alumni of the class have started more than 150 companies over the years. Halliday also received support from the MIT Energy Initiative.

"MIT tries to pull these great ideas out of academia and get them into the world so they can be valued and used," Halliday says. "For the Climate and Energy Ventures class, outside speakers showed us every stage of company-building. The technology roadmap for our system is shoebox-sized, shipping container, one-bedroom house, and then the size of a building. It was really valuable to see other companies and say, 'That's what we could look like in three years, or six years."

From startup to scale up

When Mantel was officially founded in 2022 the founders had their shoebox-sized system. After raising early funding, the team built its shipping container-sized system at The Engine, an MIT-affiliated startup incubator. That system has been operational for almost two years.

Last year, Mantel announced a partnership with Kruger Inc. to build the next version of its system at a factory in Quebec, which will be operational next year. The plant will run in a two-year test phase before scaling across Kruger's other plants if successful.

"The Quebec project is proving the capture efficiency and proving the step-change improvement in energy use of our system," Halliday says. "It's a derisking of the technology that will unlock a lot more opportunities."

Halliday says Mantel is in conversations with close to 100 industrial partners around the world, including the owners of refineries, data centers, cement and steel plants, and oil and gas companies. Because it's a standalone addition, Halliday says Mantel's system doesn't have to change much to be used in different industries.

Mantel doesn't handle CO2 conversion or sequestration, but Halliday says capture makes up the bulk of the costs in the CO2 value chain. It also generates high-quality CO2 that can be transported in pipelines and used in industries including the food and beverage industry - like the CO2 that makes your soda bubbly.

"This is the solution our customers are dreaming of," Halliday says. "It means they don't have to shut down their billion-dollar asset and reimagine their business to address an issue that they all appreciate is existential. There are questions about the timeline, but most industries recognize this is a problem they'll have to grapple with eventually. This is a pragmatic solution that's not trying to reshape the world as we dream of it. It's looking at the problem at hand today and fixing it."